Method and apparatus for assembling an expandable media filter with spacing ribbons

ABSTRACT

An expandable media filter structure is composed largely of biodegradable materials and is environmentally disposable. A plurality of pleated panes are interconnected at their edges so as to be collapsible for storage and shipping purposes but expandable for installation and use. A plurality of ribbons are ultrasonically welded to each of the panel edges, with the ribbon portions between edges being of substantially equal lengths, thereby maintaining equal spacing between the panel edges when the filter is in the expanded condition but allowing an easy collapsing of the filter for storage. Forming a part of the disposable filter are pair of end plates, with each being adhesively attached to an end panel and having a pair of slots formed near their ends for attachment to a nondisposable support structure. The end panels are formed of multiple layers of paperboard which are adhesively bonded and compressed into a U-shaped structure that rigidly supports the filter in its expanded condition. The nondisposable support structure includes a pair of molded plastic side caps that fit over the respective ends of the filter panels and the end plates. Each side cap has a pair of flanges at its opposite ends which act to maintain the filter in its expanded condition when the end pates are placed in abutting position therewith. Each side cap also includes a boss which fits into a respective end plate slot to hold the end plates in their installed positions within the side caps.

BACKGROUND OF THE INVENTION

The invention relates generally to air filters and, more particularly,to expandable air filters for use in furnaces.

The use of disposable air filters in the air distribution system of abuilding has provided an efficient and economical method of removingundesirable particulate matter from the air. In its simplest form, arectangular piece of filter media material is mounted in a cardboardframework, with the combination then being mounted in a filter cabinetor an air duct somewhere in the air distribution system. With a hot airfurnace, it is common practice to place the filter in a filter cabinetjust upstream of the fan so as to filter the return air as it enters thefurnace from the return air duct. When the filter is spent, i.e. when ithas collected a sufficient amount of particulate matter as to beconsidered “full”, then it is removed and replaced with a new filter.

One way to increase the surface area of a filter is to make itmulti-dimensional, with a plurality of accordion-like pleats. Such apleated media filter is thicker than a non pleated filter and thereforeprovides more active surface area, making it more effective and longerlasting. It can be rechargeable, i.e. cleanable, or disposable dependingprimarily on the type of material used for the filter media. Adisposable material, however, tends to be less durable and strong, andmany such materials will not be suitable for providing the necessarysupport structure that is necessary to secure and maintain the installedposition of the disposable portion of the filter in the nondisposablesupport framework. Further, a homeowner should be able to simply andeasily remove, replace and dispose of a dirty filter.

It would also be desirable for a serviceperson to have a single sizedfilter which can be used to accommodate various sizes of cabinetopenings, such that his inventory can be substantially reduced to.Generally there are three sizes of filters that must be stocked andcarried in order to meet the various installation requirements.

A pleated filter element may be selectively collapsed for storage andshipping purposes and then later expanded for installation and use. Toaccomplish this, it is necessary to provide some means to maintain thefilter element in its expanded condition. It is also desirable tomaintain substantially uniform spacing and angling of the pleats, and acomb-like, rigid framework has been used for that purpose.

It is therefore on object of the present invention to provide animproved furnace air filter and method of manufacture. That object andother features and advantages will become more readily apparent uponreference to the following descriptions when taken in conjunction withthe appended drawings.

SUMMARY OF THE INVENTION

Briefly, in accordance with one aspect of the invention, a plurality ofribbons are placed on either side of the pleated filter element and aresecured to the edges of the pleated panels with equal lengths of ribbonportions between the respective pleated panel edges such that, when thefilter element is expanded, the expanded ribbon portions cause a uniformspacing and angling of the pleated panels to occur. An end plate isattached to each of the two end filter panels, and the ribbons areexpanded and attached to the end plates.

In accordance with another aspect of the invention, the ribbons aresecured to the pleated panel edges by way of ultrasonic welding. Such aprocess provides for an efficient, economical, and effective method ofbonding the ribbons to the panel edges.

By yet another aspect of the invention, the filter element is maintainedin its expanded condition by a pair of side caps which form theframework for, and to which the two end plates of the filter element areattached. The side caps each have a pair of spaced flanges over whichthe respective filter element end plates are stretched so as to maintaina minimum expanded length of the filter element, and a pair of bossesengage with corresponding slots in the end plates to hold them in theirinstalled positions.

In accordance with still another aspect of the invention, the endplates, which form part of the disposable portion of the filter, areformed of a plurality of laminated layers which are adhesively bondedand compressed together into a U-shaped structure that provides thenecessary strength and rigidity to support the expanded filter in itsinstalled position.

By a further aspect of the invention, the end plates do not form anintegral part of the of the disposable filter element and include hangerelements which permit the storage of unexpanded portions of the filterit, such that a single sized filter can be used for multiple sizedopenings, with the unneeded portions thereof being stored within the endplates.

In the drawings as hereinafter described, a preferred embodiment isdepicted; however, various other modifications and alternateconstructions can be made thereto without departing from the true spiritand scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, perspective view of the filter structure inaccordance with the present invention.

FIG. 3 is an exploded, perspective view of a portion of the filterstructure in accordance with the present invention.

FIG. 2 is a sectional view of an side cap portion of the filterstructure as seen along lines 2—2 of FIG. 1.

FIG. 4 is a sectional view of a portion of the side cap with a filterelement installed therein.

FIG. 5 is a sectional view of an alternative embodiment of a side capportion of the filter structure.

FIG. 6 is a schematic illustration of an ultrasonic bonding process usedin the manufacture of the filter structure in accordance with thepresent invention.

FIG. 7 is a partial perspective view of an end plate portion of thefilter assembly in accordance with the present invention.

FIG. 8 is a partial perspective view of a modified embodiment of the endplate portion of the filter.

FIGS. 9 and 10 are schematic illustrations of the filter element asinstalled in a modified embodiment of the end plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an air filter structure is shown generally at10 as comprising a media filter element 11, a pair of end plates 12 and13, and a pair of side caps 14 and 16. The side caps 14 and 16 areformed of a plastic material and are reusable, whereas the combinationof the media filter element 11 and its associated end plates 12 and 13are made of polypropylene and cardboard materials, respectively, and areintended to be disposable and replaceable at the time when the filter isconsidered to be “full” or “dirty”.

The side caps 14 and 16 are identical and comprise a substantiallyplaner base element 17, normally extending sidewalls 18 and 19, andnormally extending end walls 21 and 22, the combination of which definesa cover for receiving one end of the filter element 11 as will bedescribed hereinafter. As part of the base element 17 of each of theside caps 14 and 16, of there are provided a pair of spaced handles orgrips 23 and 24 which are molded into the base element 17 as shown.Also, on the outer surfaces of the end walls 21 and 22, there areprovided a pair of molded clearance ribs 26 and 27 which serve to reducesliding friction when the filter assembly is being installed into itsoperating position within a duct or the like.

As shown in FIG. 1 and also in FIG. 2, the side caps 14 and 16 eachinclude at each end thereof a pair of spacer flanges 28 extendingnormally from the base element 17 and a locking boss 29 on the innerside of the end walls 21 and 22. Each of the spacer flanges 28 includesa beveled portion 31 angled inwardly from the wall, 21 and 22,respectively, as shown in FIG. 2. The spacer flanges 28 are designed toestablish and maintain the proper expanse of the filter element 11 whenit is installed into the unit in the expanded state, whereas the lockingbosses 29 are provided to secure the filter element in its installedposition within the side caps 16 and 17 as will be more clearlyexplained hereinafter.

Referring now to FIG. 3, the media filter 11 and its associated endplates 12 and 13 are shown in greater detail. The media filter 11comprises a plurality of pleats 32, with adjacent pleats 32 having theiredges 33 integrally connect in accordion-like fashion so as to becollapsible into a tightly stacked condition for storage and shipping,or expandable into an open position as shown for installation and use.The one ends 34 of the various pleats 32 form a plane, and the otherends 36 of the pleats 32 form another plane. The pleats 32 are formed ofa porous material which will readily allow the passage of airtherethrough with little pressure drop while filtering out any solidparticles that may be contained within the flowing air. The materialsare preferably relatively inexpensive and biodegradable since thisportion of the assembly is designed to be disposable. Any suitablematerial may be used, but a preferred material is polypropylene.

Attached to the edges 33, on each side of the pleats 32 are a pluralityof flexible spacer elements 37 which are connected to the edges 33 ofthe pleats 32 so as to allow a collapsing of the media filter element 11for storage and transport, and for the maintenance of a proper spacingof the pleats 32 when the filter element in 11 is in its expandedcondition. That is, the spacer elements 37 are so attached to the pleatedges 33 that when the spacer elements 37 are in their expandedcondition, the pleat edges 33 are uniformly spaced from their associatedadjacent pleat edges 33, and when the filter element 11 is collapsed,the spacer elements portions between the pleat edges 33 will go slackand not interfere with the collapsing of the filter element 11. Thespacer elements 37 can be of any flexible material but are preferably inthe form of a strand, string, ribbon, or the like, that can be readilyand securely affixed to the pleat edges 33 to accomplish the spacingfunction intended. For purposes of description, the spacer elements 37are shown as ribbons. A preferred material is one which is relativelyinexpensive, of reasonable strength and durability, and isbiodegradable, as this is part of the disposable portion of thestructure.

The manner in which the spacer elements are affixed to the pleat edges33 may vary in accordance with the needs and facilities of themanufacture. One approach would be to use an adhesive, while anotherwould be to stitch the elements together. A preferred approach is to useultrasonic bonding for that purpose as will be described more fullyhereinafter.

The number and location of the spacer elements 37 may also be varied inaccordance with the needs and desires of the manufacturer. Although thefilter element 11 is shown with three equispaced elements on each sideof the filter element 11, that number and location may be increased ordecreased as desired. However, in order to accommodate ease ininstallation, it is preferable to have at least one spacer elements 37on each side of the filter element 11. In addition to attaching thespacer elements to the pleat edges 33, it is also desirable, forpurposes of durability, to attach the spacer element overhangs 38 ateach end of the spacer elements 37 to the outer side of the respectiveend pleats 41 and 42 as shown in FIG. 3.

Continuing with the description of FIG. 3, the end plates 12 and 13 areidentical and are generally U.-shaped in form, having a body element 43and two normally extending side elements 44 and 46. Formed in each endof the body 43 is a slot 47 which is used for securing the filterelement 11 in its installed position within the side caps as will bemore fully described hereinafter. Although the end plates 12 and 13 maybe formed of a molded plastic material, or the like, a preferredmaterial is cardboard because of its relatively low-cost andbiodegradability. The use of such material for this purpose, however,poses certain problems which were solved in a manner to be describedmore fully hereinafter.

The end plates 12 and 13 are part of the disposable filter structure 10and as such are securely fastened to the respective end pleats 41 and 42by an adhesive or the like. That is, the entire outer side 39 of each ofthe end pleats 41 and 42 are preferably glued to the inner sides of therespective body elements 43 of the end plates 12 and 13. In doing so,the spacer element overhangs 38 are also captured between the twoelements to thereby provide a durable union which remains together forthe life of the filter structure 10. The end plates 12 and 13, withtheir side elements, therefore serve to encase the collapsed mediaduring storage and shipment and to facilitate and maintain expansion ofthe media during installation and operation.

Having described both the disposable filter portion, i.e. the filterstructure 10 as shown in FIG. 1, and the reusable side caps 14 and 16into which they are installed, the manner in which the disposableportion is installed within the side caps will now be described as shownin FIG. 4. To install a disposable filter element, a collapsed filterstructure 10 is removed from its packaging and expanded to a fully openposition, with the spacer elements 37 being extended to theirfull-lengths. When the filter structure 10 is in its fully expandedcondition, the separation of the end plates 12 and 13 should be suchthat they should be able to be easily installed in the space between thespacer flange 28 and end wall 21 or 22. That is, the side elements 44and 46 of each of the end plates 12 and 13 should slide over the beveledportion 31 and onto the spacer flange 28 as shown in FIG. 4. When in thefully installed position, the body element 43 will be fully engaged withthe inner side of the end wall 21, such that the boss 29 slips into theslot 47 to secure the filter structure 10 within the side cap. In thisposition, the pleat ends 34 and 36 are captured in an interference fitwithin the boxlike structure of the side caps 14 and 16 to form acomposite sealed unit which can now be installed in its desired positionwithin a duct or the like. When the filter becomes dirty, the entireassembly can be removed to replace the disposable filter structure 10.Removal can be easily accomplished by slightly compressing the endplates 12 and 13 together so as to disengage the boss 29 from the slot47 and allow the filter structure 10 to be removed from the side caps 14and 16.

FIG. 5 shows an alternative embodiment of an side cap 17 wherein, on theouter side thereof, an extended edge is molded around entire perimeterand is seen as a pair of border ribs 48 and 49 which are integrallymolded at the respective ends of the side cap 17. The purpose of theribs 48 and 49 are to extend the depth of the filter assembly to fit adeeper cabinet. In this way, a single filter size may be used incabinets of various depths by simply changing the side caps, with theside caps selected having ribs 48 and 49 which are of the appropriatelength to extend across the depth of the cabinet.

As mentioned hereinabove, the spacer elements 37 are secured to thepleat edges 33 by way of an ultrasonic bonding process. That processwill now be described with reference to FIG. 6. A conveyor belt orcontinuous chain 51 with a sawtooth form corresponding to the size andshape of the pleated filter material is provided as shown, with motordrive means (not shown) to cause it to rotate in a clockwise direction.A first ultrasonic welder 52 is provided on the upper side of theconveyor belt, and a first backup device 53 is provided below theconveyor belt, opposite the welder 52. This welder is used toultrasonically bond the spacer elements 37 to the upper side of themedia filter material as it passes through the welding apparatus.Similarly, a second ultrasonic welder 54 located below the conveyorbelt, and a second backup device 56, located above the conveyor belt,are used to ultrasonically bond the spacer element 37 to the oppositeside of the media filter material.

As a first step in the process, the filter media goes through alaminating process wherein a wire mesh support is attached to one sidethereof, with the combination then going through a pleating machine toform pleats to the desired depth. This is a common process in themanufacture of pleated filters. The pleated media 11 is then fed intothe welding apparatus from the left side thereof, in an expandedcondition, as shown. As it proceeds along the conveyor belt, the ribbonswhich act as spacer elements 37 are then introduced on each side of themedia as shown. Thus, an upper ribbon 57 coming off of a spool 58 isextended along the upper side of the expanded pleated material, and alower ribbon 59 coming off of a spool 61 is extended along the lowerside of the expanded pleated material. As the edges of the pleatedmaterial, with its overlaid ribbon, pass through the welding apparatus,the two welders operate to ultrasonically weld the ribbon to each edgeof the media material. This is accomplished on the upper side, forexample, by the backup device 53 being pneumatically raised to aposition directly below the peak or edge of the pleated material toprovide support thereof, and the welder 52 being pneumatically loweredto momentarily engage the ribbon and press it against the edge of thepleated material. During engagement, the welder 52 causes ultrasonicvibrations within both the ribbon and the pleated material, therebycausing both of them to heat up and bond to each other. The backupdevice 53 is then retracted, the welder is raised slightly, and in thepleated material is advanced to the next edge so that in the process canbe repeated. Meanwhile, the same process is occurring at the other(lower) side of the media material by the welder 54 and backup device56. The result is a pleated material being delivered at the right sideof the welding apparatus, with ribbons 57 and 59 being attached to eachedge thereof so as to thereby establish a uniform maximum spacing of thepleats when in the expanded condition. That expanded filter material canthen be cut to the desired length, attached to end plates at either endthereof, and then be collapsed for storage and shipping.

Whereas the process as just described was applied to bond a singleribbon on each side of the media material, it will be understood thatthe same process can be extended to simultaneously weld a plurality ofribbons on each side of the media material. Also, even though theprocess as described includes the steps of expanding the media andextending the ribbon across the expanded edges, it is also possible topresent the pleated material in a collapsed or partially collapsedcondition for the welding process. This approach would require a similarcollapsing of the ribbon in order to obtain the proper spacingrelationship with the pleat edges, but may allow the simultaneouswelding of a plurality of edges with a single welder.

Having generally described the end plates 12 and 13 in design andfunction, the specific design structure will now be described withreference to end plate 13 as shown in FIG. 7. As will be seen, the endplates are constructed of a plurality of layers 62 of a natural fibrousmaterial such as paperboard or cardboard, with the layers 62 beinglaminated by bonding and compressing at high pressures the individuallayers into the final U-shaped form to provide a rigid, strong anddurable structure that will withstand the demands of intended use. Asuitable structure has been found to result from the use of 6-10 layersof approximately 0.015 in. thickness paperboard that are adhesivelybonded together with a water-based glue. The outer layer may have a claycoating in order to obtain a low-cost, high contrast, white surface forthe printing of instructions and other information.

Such a laminated construction of the end plates provides the strengthand rigidity to prevent sagging of the unsupported middle portionthereof, and its shape retention capability facilitates the easyinsertion into and locking into place within the side caps as describedhereinabove. At the same time, it is sufficiently flexible to allow itto be pushed in to unlatch it from the side caps for purposes ofreplacement. The natural materials from which it is made arebiodegradable and therefore easily disposable.

Referring now to FIG. 8 an alternative embodiment of the end plate isshown at 63 to include a body element 64, side elements 66 and 67, andhangar elements 68 and 69 to form a C-shaped element. A slot 71 isformed in the body element 64, at each end thereof, in the same way asdescribed hereinabove with respect to end plates 12 and 13. However,here the end plate 63 does not form an integral part of the disposablefilter assembly but is rather a nondisposable part that is used not onlyto support the disposable media filter element 11 but also toselectively provide a storage container for portions thereof in order toaccommodate the needs of an installer in meeting the requirements ofmultiple sized openings. This will be more clearly seen with referenceto FIGS. 9 & 10.

If a service person can carry a single filter size for installation invarious sized cabinets, he can reduce his inventory to save space andmoney. That is, filters for residential use are generally of one ofthree sizes: 16×25 in., 20×25 in., or 24×25 in. If a service person cancarry only the 24×25 in. filter and use them for all installations, itwill be to his benefit. The present design of the end plate 63 willallow this to occur. Referring to FIGS. 9 & 10, a single media filterelement 11, having dimensions of 24×25 in., for example, is used in itsentirety for installation in a 24×25 in. opening as shown in FIG. 10,and is partially used in a 16×25 in. opening as shown in FIG. 9, withthe remaining unused portion being stored in the end plates 63 as shown.

The disposable filter 11 includes no integral end plates but only theplurality of folded pleats as described hereinabove. Such a filter isinstalled into the two end plates by simply inserting the end panelsinto the respective end plates and sliding them in. This is shown inFIG. 10 wherein only a single end panel is captured within therespective end plates 63, with the hangar elements 68 and 69 providingthe necessary support to maintain the filter in its expanded conditionwhen the end plates 63 are installed into the side caps as describedhereinabove. In the FIG. 9 installation, wherein the opening is only16×25 in., a portion of the pleats 72 remain in their collapsedcondition and are collectively installed into the end plates as shown.Similarly, for use in an opening of 16×20 in., a smaller portion of thepleats 72 would remain in their collapsed condition and be inserted intothe end plates 63. In each case, however, the operative, expandedportion of the filter element 11 would be fully expanded as shown.

Since the C-shaped end plates 63 are designed for re-use, they arepreferably composed of a more robust material. Whereas it may bepossible to form the C-shaped element in a laminated material asdescribed hereinabove, a molded plastic or a light metal material ispreferred. Further, it may take various forms and still provide the samefunction. For example, the hangar elements 68 and 69 do not need to becontinuous along the lengths of the end plates 63 as shown, but onlyneed to provide support at various points along the length and cantherefore be discontinuous or simply be a plurality of brackets attachedto the side elements 66 and 67. Also, whereas the end plates 63 havebeen shown and described as open-ended to facilitate the easy insertionof the end pleats therein, they may be closed to provide greaterstrength, with the end pleats then being installed in another mannersuch as by installing one edge of the pleat and then flexing the pleatin order to install the other edge thereof.

What is claimed is:
 1. A method of assembling a filter comprising the steps of: providing an expanded pleated media filter having a plurality of filter panels with adjacent panels being interconnected at their edges so as to collectively be selectively collapsed or expanded; arranging said plurality of filter panels so that adjacent edges thereof are substantially uniformly spaced at a desired interval; providing at least one flexible strand extending across and engaging only the edges of each of said panels; and ultrasonically bonding said flexible strand to each of said panel edges such that portions of said flexible strand between adjacent panel edges are all of substantially equal lengths.
 2. A method as set forth in claim 1 wherein a plurality of flexible strands are provided to extend across and engage the edges of each of said panels, and each of said plurality of flexible strands are ultrasonically bonded to each of said panel edges.
 3. A method as set forth in claim 1 wherein at least one flexible strand comprises a pair of strands with each strand extending across and engaging the edges of each of said panels, with said pair of strands being on opposite sides of said panels.
 4. A method as set forth in claim 1 wherein said flexible strand is a ribbon.
 5. A method as set forth in claim 1 wherein said filter panels are made from a polypropylene material.
 6. A method as set forth in claim 1 wherein said flexible strand is made from a polypropylene material.
 7. A method as set forth in claim 1 wherein said arranging step includes the step of expanding said plurality of filter panels, and further wherein the step of providing a flexible strand across the edges of each of said panels includes the step of extending said flexible strand to its maximum length.
 8. A filter assembly comprising: an expandable pleated filter element having a plurality of filter panels with adjacent panels being interconnected at their edges; and at least one flexible strand extending across and ultrasonically bonded to each of said edges such that those portions of flexible strand between adjacent edges are not bonded and are of substantially equal lengths.
 9. A filter assembly as set forth in claim 8 wherein said at least one flexible strand comprises a plurality of flexible strands.
 10. A filter assembly as set forth in claim 1 wherein at least one flexible strand comprises a pair of strands with each strand extending across and being ultrasonically bonded to the edges of each of said panels, and said pair of strands being on opposite sides of said panels.
 11. A filter assembly as set forth in claim 8 wherein said flexible strand is a ribbon.
 12. A filter assembly as set forth in claim 8 wherein said filter panels are made from a polypropylene material.
 13. A filter assembly as set forth in claim 8 wherein said flexible strand is made from a polypropylene material. 